Shein Group Ltd. has begun offering other fashion brands access to its apparel manufacturing network in China as a service, people familiar with the matter said, as it seeks new revenue streams amid pressure on its retail business from US tariffs.Other fashion brands can now tap on the fast-fashion retailer’s supply chain, which includes factories that can turn around new designs in 5-7 days, as long as they open a store on its online marketplace, said the people, who asked not to be identified ...